Effect of D on the evolution of radiation damage in W during high temperature annealing

The effect of deuterium (D) on the annealing of radiation damage was studied. Tungsten (W) samples were sequentially irradiated with 20 MeV W ions at room temperature and loaded with a low-temperature D plasma at 370 K to decorate the created defects. After this, half of each sample was W irradiated at room temperature again to create additional radiation damage. To study the evolution of the created defects with D being present, samples were annealed by heating them to a desired temperature and held for 2 h. The surviving displacement damage was decorated by re-exposing the samples to the same D plasma as before. At various steps of the experiment the D depth profiles were measured using nuclear reaction analysis and after the last re-exposure a thermal desorption spectroscopy analysis was done to determine the D desorption spectra.D release is dominated by two desorption peaks centred at 520 K and 780 K for a 3 K min−1 temperature ramp. For temperature holds below 500 K no measurable change in the intensity of the desorption peaks was measured. For temperature holds above 500 K, the low temperature D desorption peak started to reduce in intensity. The high temperature D desorption peak showed signs of evolution only for temperature holds above 600 K. This behaviour was independent of the number of W irradiations used.A macroscopic rate equation model was used to recreate the experimental results. Using the fill-level dependant D-defect interaction picture we were able to determine that three distinct defect types with several fill-levels each are sufficient to describe the results. The concentrations of defect 1 (vacancies) and defect 2 (small vacancy clusters) reduced by 50% and 35%, respectively, after an 800 K temperature hold. No reduction was found for defect 3 (large vacancy clusters).